Lightweight Gear Resin Coupling to Prevent Fatigue Fracture
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Solution Overview
Problem
Existing lightweight gears face challenges in reducing weight while maintaining strength, particularly due to stress concentration at corners of irregularities, which can lead to fatigue fracture during long-term operation, especially when using strong resin materials.
Innovation Solution
A lightweight gear design featuring an annular metal tooth portion and metal shaft coupled with a resin coupling element, where the joining parts have irregularities with rounded corners to reduce stress concentration, and the coupling element is made of a thermoplastic resin with a thin thickness and through-holes for weight reduction, enhancing the anchor effect and surface hardness through heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the coupling element is made of strong resin material to reduce weight, then weight reduction is achieved, but stress concentration occurs at corners of irregularities leading to fatigue fracture
Solution Approach 1:
The corners of the irregularities in the coupling element are rounded instead of being sharp, which eliminates stress concentration points. This curvature modification allows the use of strong resin materials for weight reduction while preventing fatigue fracture at the corners during long-term operation.
2Weight of moving object
If the coupling element thickness is reduced to achieve weight reduction, then weight is reduced, but strength and stress resistance deteriorate
Solution Approach 1:
Rounding the corners of the irregularities prevents stress concentration, which allows the coupling element to be made thinner without compromising strength. The curved corners distribute stress more evenly, enabling weight reduction through thickness reduction while maintaining adequate strength.
3Power
If irregularities with sharp corners are used for engagement, then torque transmission is improved, but stress concentration leads to fatigue fracture
Solution Approach 1:
The irregularities are designed with rounded corners that maintain effective engagement for torque transmission while eliminating the sharp corners that cause stress concentration. This allows the gear to transmit torque efficiently without suffering from fatigue fracture at the irregularity corners.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design effectively reduces weight while preventing excessive stress concentration, allowing for a thinner coupling element and improved strength, enabling efficient torque and force transmission with reduced parts and machining costs, and enhancing durability and oil resistance.
Implementation Method 1
corners of the irregularities are rounded to release a stress
Implementation Method 2
enhancing the anchor effect and surface hardness through heat treatment
Data Source
AI summary
A light-weight gear including: an annular tooth portion made of metal; a shaft extending along a central axis of the tooth portion and made of metal; and a coupling element configured to couple the shaft to the tooth portion and made of a resin, in which a joining part between the shaft and the coupling element and a joining part between the tooth portion and the coupling element are provided with irregularities configured to be engaged with one another in a circumferential direction, and corners of the irregularities are rounded to release a stress. Also, provided is a manufacturing method of a light-weight gear including: disposing the tooth portion and the shaft in a mold and injecting a molten resin into a cavity of the mold, thereby simultaneously performing injection molding of the coupling element and joining the coupling element to the tooth portion and the shaft.